1. Field of the Invention
The present invention relates generally to heaters for printing presses and in particular to a heater with infrared quartz tube heat lamps for drying printed material in sheet-feed and envelope presses.
2. Description of the Prior Art
In certain types of printing operations, it is desirable to dry the printing ink more quickly than would occur if the printed material were merely exposed to the ambient atmosphere. Generally, higher quality printing work tends to require such supplemental drying. For example, color work with a glossy finish printed on a high quality of paper requires supplemental drying to avoid smearing the ink. Newspapers, on the other hand, are typically printed on webs of relatively low-quality paper which rapidly absorbs the ink and thus may not require supplemental drying.
Various methods have heretofore been employed for supplemental drying of printed materials. For example, the freshly-printed material can be sprinkled with anti-offset powder for absorbing the liquid solvents. Although this method consumes relatively little energy, the excess powder tends to disperse widely so that the press area may require frequent cleaning.
Convection heaters have also been used for drying printed materials and generally involve passing heated air over the printed material. However, convection drying is relatively inefficient and presents the problem of disposing of the solvent-laden exhaust air, which may contain unacceptable levels of environmental pollutants. Also, many convection heaters are too large or expensive for relatively small printing presses and installations where space is limited.
The aforementioned problems can be at least partly overcome by using radiant heaters or lamps for drying the printed materials. A relatively high percentage of the radiant energy generated thereby is transmitted through the atmosphere and absorbed by liquids and solids. Thus, for drying printed materials, radiant drying systems have been found to be more efficient than convection systems because with the latter much of the thermal energy is lost to the atmosphere, whereas with the former most of the radiant energy is absorbed by the printed material and the ink. Radiant energy can be directed to the printed material by reflectors to further increase efficiency.
Radiant energy in the short to medium wave length infrared range (i.e. about 0.75 to 1.50 and 1.50 to 3.00 microns respectively) is effective for drying printed material. Quartz tube heat lamps, for example, may be employed to produce such energy. They tend to be well suited for the requirements of the printing industry because they are relatively efficient and reasonable in cost.
Furthermore, quartz tube heat lamps tend to have relatively low thermal masses so that they heat up and cool down relatively quickly. This attribute is important for drying printed materials because in some heaters the heat lamps are operated only when the presses are actually running. A relatively low thermal mass allows a heat lamp to rapidly attain its operating temperature and correspondingly cool down quickly enough to avoid igniting the stationary printed material present in the drying area of the press when it stops. Quartz tube heat lamps have yet another advantage in that their output can be relatively precisely controlled by varying the electrical current input thereto.
Quartz tube heat lamps have heretofore been used for drying printed materials. Prior art examples of such systems are found in the Hanson U.S. Pat. No. 2,065,070; the Early et al. U.S. Pat. No. 3,159,464 and the Visser U.S. Pat. No. 3,122,999.
Yet another example is shown in the Jacobi, Jr. et al. U.S. Pat. No. 4,501,072 which is assigned to a common assignee herewith. In the Jacobi, Jr. et al. '072 patent, heater panel assemblies with multiple quartz tube heat lamps are provided in a heater and are movable between open and closed positions. When a moving web of printed material is passing through the heater, the heater panel assemblies are relatively close thereto and the web is dried by radiant energy from the quartz tube heat lamps. If the web stops moving, e.g. when the press stops or the web breaks, the heater panel assemblies automatically retract to positions spaced from the web and the quartz tube heat lamps are extinguished.
Relatively small printing presses, e.g. for envelopes and sheets, often lack supplemental drying capabilities due to space limitations. Furthermore, even where sufficient space exists for the installation of a quartz tube heat lamp, the infrared radiation can interfere with the press operation by drying the ink on the impression cylinder unless means are provided for deflecting or exhausting such radiant heat away from the impression cylinder and, preferably, towards the printed material.
Heretofore there have not been available heaters for drying materials in printing presses and the like, especially relatively small sheet-feed and envelope presses, with the advantages and features of the present invention.